To the Editor.—The CASE REPORT entitled "Hypokalemic Respiratory Arrest in Diabetic Ketoacidosis"1 emphasizes the importance of adequate potassium repletion in the treatment of patients with diabetic ketoacidosis. However, we were surprised that no mention was made of the need also to assess magnesium concentrations in such patients. Hypomagnesemia is a common finding in diabetics,2 especially those recovering from diabetic ketoacidosis,3 and has been reported to cause a decrease in respiratory muscle power.4 Moreover, refractory hypokalemia, as was seen in the case reported, can be caused by magnesium deficiency.5 Hypophosphatemia is also commonly associated with hypomagnesemia.6Renal losses of magnesium secondary to glycosuria play a primary role in the pathogenesis of magnesium depletion in diabetics.2 Intravenous fluid therapy during treatment of diabetic ketoacidosis aggravates urinary magnesium losses, and insulin therapy also tends to lower the serum magnesium concentration.3,7 Less than 1% of